Reward context sensitivity impairment following severe TBI: an event-related potential investigation.

Many rehabilitation protocols following traumatic brain injury (TBI) utilize reinforcement and reward to influence behavior and facilitate recovery; however, previous studies suggest survivors of severe TBI demonstrate impairments in contingency utilization and sensitivity. The precise neurobiological mechanisms underlying these deficits have not been thoroughly explored, but can be examined using the "feedback-related negativity" (FRN)--an event-related potential (ERP) component evoked following performance or response feedback (e.g., whether a monetary reward is obtained) with a larger FRN following unfavorable than favorable outcomes--particularly when unfavorable feedback occurs in the context of high reward probability. We examined ERPs elicited by favorable (monetary gain: "reward") and unfavorable (no monetary gain: "non-reward") feedback during a guessing task where probability of reward outcome was manipulated in survivors of severe TBI and demographically matched healthy participants. Consistent with previous findings, controls showed larger amplitude FRN to non-reward feedback and the largest amplitude FRN following a non-reward when reward probability context was greatest. In contrast, FRN in TBI participants did not significantly differentiate non-reward from reward trials and their FRN was largest to reward trials in the low reward probability context. Findings implicate an electrophysiological marker of impaired reward context sensitivity following severe TBI.

Cognitive control impairments in traumatic brain injury.

The componential nature of impaired cognitive control following traumatic brain injury (TBI) remains uncertain. We examined regulative and evaluative components of cognitive control in mild and moderate-to-severe (M/S) TBI patients and demographically-matched comparison participants using the AX-CPT task. We also examined relationships of cognitive control impairment to ratings of cognitive, behavioral, and affective symptomatology on the Dysexecutive Questionnaire (DEX). Results revealed that M/S, but not mild TBI patients showed deficits in context-processing and post-error strategic adjustments -- extent of impairments correlated with TBI-related symptomatology. Thus, patients with M/S TBI evidence cognitive control dysfunction in the processing and active maintenance of context representations.